Abstract: The cross section for $e^+ e^- \to π^+ π^- J/ψ$ between 3.8 GeV and
5.5 GeV is measured with a 967 fb$^{-1}$ data sample collected by the Belle
detector at or near the $Υ(nS)$ ($n = 1,\ 2,\ ...,\ 5$) resonances. The
Y(4260) state is observed, and its resonance parameters are determined. In
addition, an excess of $π^+ π^- J/ψ$ production around 4 GeV is
observed. This feature can be described by a Breit-Wigner parameterization with
properties that are consistent with the Y(4008) state that was previously
reported by Belle. In a study of $Y(4260) \to π^+ π^- J/ψ$ decays, a
structure is observed in the $M(π^\pm\jpsi)$ mass spectrum with $5.2σ$
significance, with mass $M=(3894.5\pm 6.6\pm 4.5) {\rm MeV}/c^2$ and width
$Γ=(63\pm 24\pm 26)$ MeV/$c^{2}$, where the errors are statistical and
systematic, respectively. This structure can be interpreted as a new charged
charmonium-like state.